AW4 malfunction

89, I6, a/t

Not getting 2nd gear or T/Q lockup. I can override C14 and C15 to force 2nd gear and T/Q lockup, so I know the trans works. New TPS started the 2nd gear issue, before that T/Q was not locking. Now both problems. Swapped TCU today, no change, in fact can disconnect the TCU and its the same sequence. Brake switch appears OK.

Possible that replacement TCU is bad also. What else am I missing?

The TPS is suspect. Test it. Replace it with an OEM Jeep TPS.

Numerous posting provide plenty of evidence that the cheap TPS sold at the big name parts stores are often of poor quality and either fail quickly or are defective right out of the box.

Clean, adjust, or replace the NSS.

The TPS and the NSS both have direct input to the TCM and PCM for shifting the AW-4.

RENIX TPS
(Thanks to Joe Peters from for this information)

MANUAL TRANSMISSION:

RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector. Wire "A" is positive. Wire "D" is ground. Remove the three-wire connector from the TPS. Key ON, measure voltage from "A" positive to "D" ground. Note the voltage reading--this is your REFERENCE voltage. Now, reconnect the three-wire connector to the TPS. Key ON, back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. Adjust the TPS until you have achieved this percentage, if you can't achieve the correct output voltage replace the TPS and start over.

AUTOMATIC TRANSMISSION:

RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES. However, the automatic TPS also has a four-wire connector. For the automatic transmission equipped vehicles the four-wire connector provides data to the TCU. Disconnect the four-wire connector. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Now, reconnect the four-wire connector to the TPS. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. Adjust the TPS until you have achieved this percentage, if you can't replace the TPS and start over.

So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire connector side of the TPS. If you have ENGINE issues check the three-wire connector side of the TPS.

For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.

Solenoids, that was the problem in my 96 when the Torque Converter wouldn't lock, I replaced them and so far (knock on wood) the lock up has worked fine

1984jeep said:

Solenoids, that was the problem in my 96 when the Torque Converter wouldn't lock, I replaced them and so far (knock on wood) the lock up has worked fine

Click to expand...

Except that in this case the solenoids work when I activate them manually. Give them the volts and they work, transmission shifts into appropriate gear and TC will lock.

AKAIK, there is no signal (voltage) coming out of the TCU to activate the solenoids. We followed the factory procedure to adjust the TPS and it is right on the recommended voltage. I will look into the NSS, but I dont know how that affects second gear or TC lock. We are going to reinstall the original TPS which we had no firm reason to replace (except the mechanic throwing my money at it).

Thanks